The OSR started about eight years ago, with the sudden interest in publishing the first round of retro-clones, OSRIC, BFRPG, and hot on their heels Labyrinth Lord, followed soon after by Swords & Wizardry.
Cue the slew of other retro clones, both of various versions of D&D and of other old school games.
The second wave included new imaginings of what might have been, and new/old systems that merged more modern design elements with classic game play. Correct me if I'm wrong, but I think Mazes & Minotaurs, with its "what if Bullfinch, Hamilton and Graves had inspired Gygax and Arneson more than Howard, Tolkien and Lieber?" motif, was the first of the second wave games.
I just downloaded yet another free old school game on pdf. It's over 400 pages, and really, most of the stuff I'd probably use from it will be any new monsters, maybe a class or race, possibly some magic items.
I really don't need the "rules" anymore.
Now, don't get me wrong. There will always be room for complete rulebooks. New gamers need them. Old gamers sometimes appreciate only needing one book. Game writers want to feel that their game is complete and "all you need." I get that.
But if I were to download a document with just the basic information for players: race, class, spells, equipment, and any special rules necessary, maybe a bestiary if it's sci-fi or non-European/D&D-goulash, plus some setting/milieu/genre information, I could run the game.
Will this be the next phase of the OSR? Supplemental rulebooks that bolt onto your favorite rule set to change the flavor/setting a bit, but otherwise follow the rules of the parent game? Some publishers would actually create both a full version and a cut down "stage three" version. Maybe give away the Stage Three supplement for free, and sell the whole rulebook for those who like to consult a single volume when they play?
Long story short, I'm thinking a1) I don't need to download any more 400+ page rulebooks of what is basically the same game, even if they're free. I've already got my Franken-D&D rules the way I like them. b2) Chanbara is likely going to end up like this. I don't have time to rewrite all the rules for the whole game, at least not if I'm going to release it any time soon. I'll give you enough info to make your character and to create a weird mytho-Japan setting. You'll need to use your favorite version of Ye Olde Game for the rest.